In the operation of seeding, seeds are transferred from a hopper and deposited uniformly in the soil. In one type of seeding machines the seeds are pulled by gravity through a flow control mechanism attached to the bottom of the hopper. This mechanism consists of a set of two plates: one plate, having a plurality of holes sized slightly larger than the seed, is made to rotate at a rate proportional to the seed discharge rate. Seeds fall into these holes and are trapped in place by a stationary plate placed below the rotating plate and having a single discharge opening. As the first plate rotates it carries the trapped seeds toward the opening in the stationary plate. The seeds then gravitates towards the soil. These types of machines are only suitable for large and uniform size seeds. An adaptation of this type of machine for use in small scale gardening is described by Beckworth in U.S. Pat. No. 4,315,580. For the purpose of sowing small or nonuniform size seeds, the power of air flow or of vacuum suction is employed. Dobson et al in U.S. Pat. No. 4,239,126 describe such a machine: the round portion of a rotating drum fits closely against the opening of a seed hopper thus making contact with the seeds. The portion of the circumference of the drum which contacts the seeds has a plurality of holes having a size smaller than the seed. Vacuum suction is applied to the drum via the center of its pivot. The suction force draws seeds towards the holes in the drum. Consequently, the holes are plugged up with seeds. If the size of the holes and the power of the vacuum is chosen properly, only one seed is picked up by each hole. As the drum rotates the picked seed is carried up, then out of the hopper and then down. A wheel which is mounted on a separate and internal pivot, is engaged to the inner surface of the drum and covers momentarily the hole that moves to the point of contact between the drum and the wheel. The suction force is thus interrupted and the seed which is held against that hole is released and falls onto the soil.
A hobbyist gardener who needs to seed a small scale back-yard garden with small seeds such as carrot or lettuce seeds can appreciate the difficulty of attempting the task of distributing the seeds manually into prepared furrows. He can of course resort to pelletized seed or seed tape which are available commercially for limited seed varieties and at a substantially greater cost. The objective of the invention is to provide the small scale gardener the means for planting small seeds with ease. The invention uses the principle of vacuum seed pickup as described above but eliminates the need for a continuous vacuum source. The power is provided by the operator who guides a wheel along a prepared furrow and the wheel rotation in turn drives the rest of the mechanism. In addition, since small seed is often indistinguishable once deposited on the soil, it is a second objective of the invention to provide the operator with an electronic monitor that gives him the assurance that seeding is indeed taking place.